<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>行高属性</title>
  <style>
    .tqjc{
      font-size: 40px;
      /* 第一种写法  normal */
      /* line-height: normal; */
      /* 第二种写法   1.5倍的font-size */
      /* line-height: 1.5; */
      /* 第三种写法   80px */
      /* line-height: 80px; */
      /* 第四种写法  百分比 */
      line-height: 150%;

    }
    /* 作用1：调整多行文字的距离 */
    #line1{
      font-size: 40px;
      background-color: skyblue;
      line-height: 100px;
    }

    /* 作用2：调整单行文字的垂直居中 */
    #line2{
      font-size: 40px;
      background-color: skyblue;
      height: 300px;
      line-height: 300px;

    }

  </style>
</head>
<body>
  <div class="tqjc">I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成</div>

  <div id="line1">I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成I have a dream.天桥嘉成</div>
  <br>
  <div id="line2">I have a dream.天桥嘉成I have a dream.</div>

  
</body>
</html>